Vitamin D Linked To Osteoporosis In North American Women

October 3, 2004

More than Fifty Percent of Women have inadequate Levels of Vitamin D, Despite Widespread Acceptance of Vitamin D as an Essential Part of Osteoporosis Therapy

October 3, 2004 – More than half of women currently treated for osteoporosis have suboptimal levels of vitamin D, according to new research presented today at the American Society for Bone and Mineral Research (ASBMR) meeting in Seattle. Study results demonstrated that despite routine physician recommendations that women diagnosed and treated for osteoporosis take over-the-counter (OTC) vitamin D supplementation, vitamin D inadequacy is still highly prevalent in this population. The National Osteoporosis Foundation advises getting recommended daily amounts of vitamin D and calcium as one of the five steps involved in bone health and osteoporosis prevention. More than 10 million people in the United States are estimated to have osteoporosis and 80 percent are women. Vitamin D, an essential component of osteoporosis therapy, helps to ensure that the body absorbs and retains calcium and phosphorus, both critical for building bone.

“While women may know that calcium is an important part of bone health, this research shows that some women on treatment for osteoporosis are unaware of the important role vitamin D plays or are simply not getting adequate amounts as part of their treatment regimen,” said Ethel Siris, MD, Madeline C. Stabile Professor of Clinical Medicine at Columbia University College of Physicians and Surgeons and director of the Toni Stabile Center for the Prevention and Treatment of Osteoporosis at New York-Presbyterian Hospital/Columbia University Medical Center. “Getting enough vitamin D, whether through supplements, proper food choices or appropriate and careful exposure to sunlight, is vital to managing osteoporosis.”

The study showed that prevalence of vitamin D inadequacy was significantly higher in women who took less than 400 international units (IU) of vitamin D supplementation daily compared with those who took at least 400 IU or more daily (63 percent versus 45 percent, respectively); p<0.001.* Surprisingly, the study findings showed that nearly half of the women were not getting enough vitamin D based on their serum vitamin D levels, despite 66 percent self-reporting in a patient questionnaire that they had spoken with their physician about the importance of taking vitamin D for bone health.

About the Study This cross-sectional observational study examined 1,536 postmenopausal women, averaging 71 years of age, from 61 North American sites between November 2003 and March 2004. The study was designed to describe the distribution of serum 25-hydroxy vitamin D [25(OH) D] levels in postmenopausal women currently receiving antiresorptive (e.g., bisphosphonates, SERMs, calcitonin) or anabolic therapies (e.g., parathyroid hormone) to treat or prevent osteoporosis. 25(OH) D is produced by the body from vitamin D precursors and its level in the blood serum generally indicates the level of the body’s vitamin D reserves. In this study, vitamin D inadequacy was defined as 25 (OH) D

About Vitamin D and Osteoporosis Vitamin D plays an important role in osteoporosis management by promoting calcium absorption. It enhances calcium absorption by the intestine, allowing calcium to enter the bloodstream. Vitamin D also works in the kidneys to help resorb calcium that otherwise would be excreted. Vitamin D inadequacy can lead to weak bones and an increase in the risk of fractures. Vitamin D is manufactured in the skin after direct exposure to sunlight, but as adults age, the ability to make vitamin D through the skin diminishes. Many experts recommend a daily intake of between 400 and 800 IU of vitamin D through dietary sources such as dairy products (primarily milk) and a few types of fish (e.g. salmon, mackerel) or in the form of supplements for adults over 50.

Osteoporosis, a disease characterized by low bone mass and structural deterioration of bone tissue, can lead to bone fragility and an increased susceptibility to fractures, especially of the hip and spine. Osteoporosis is often called a "silent disease" because bone loss occurs without symptoms. People may not know that they have osteoporosis until their bones become so weak that a sudden strain, bump or fall from standing height causes a fracture or a vertebra to collapse. One in two women over age 50 will have an osteoporosis-related fracture in her remaining lifetime.

Funding for this study was provided by Merck and Co. Inc.


*Located in New York City, Columbia University Medical Center provides international leadership in basic and clinical research, medical education, and health care. The medical center includes the dedicated work of many physicians, scientists, and other health professionals at the College of Physicians & Surgeons, the School of Dental & Oral Surgery, the School of Nursing, the Mailman School of Public Health, the biomedical departments of the Graduate School of Arts and Sciences, and allied research centers and institutions. The pioneering tradition of Columbia University health scientists, who have achieved some of the 20th century's most significant medical breakthroughs, continues today.


Ethel Siris, IU, OTC, United States